Merge pull request modelcontextprotocol#239 from evalstate/feature/resource-size-2

Reintroduction of "size" field for Resource

Author: jspahrsummers

schema/2025-03-26/schema.json

@@ -1553,6 +1553,10 @@
                     "description": "A human-readable name for this resource.\n\nThis can be used by clients to populate UI elements.",
                     "type": "string"
                 },
+                "size": {
+                    "description": "The size of the raw resource content, in bytes (i.e., before base64 encoding or any tokenization), if known.\n\nThis can be used by Hosts to display file sizes and estimate context window usage.",
+                    "type": "integer"
+                },
                 "uri": {
                     "description": "The URI of this resource.",
                     "format": "uri",

schema/2025-03-26/schema.ts

@@ -473,6 +473,13 @@ export interface Resource {
    * Optional annotations for the client.
    */
   annotations?: Annotations;
+
+  /**
+   * The size of the raw resource content, in bytes (i.e., before base64 encoding or any tokenization), if known.
+   *
+   * This can be used by Hosts to display file sizes and estimate context window usage.
+   */
+  size?: number;
 }
 
 /**